The present invention refers to a wheel with a suspension system. Such wheels can particularly be used in self-propelled vehicles, like wheel chairs and bicycles. Furthermore, these wheels can also be used for suspension of any rotatable mass including wheels of motorized or otherwise powered vehicles. Furthermore, the present invention refers to a centralizing unit comprising a suspension system, whereby this centralizing unit may, according to the invention, be part of a wheel.
Rotating masses tend to accommodate vibrations and shocks due to internal and/or external forces and impacts from surfaces in contact. One example is the vibratory motion of a wheel when it travels a distance on a non-purely smooth surface. Motorized and other vehicles commonly include cumbersome suspension systems in order to protect their chassis or other affiliated parts from early failure as well as to avoid unpleasant conditions to passengers.
Suspension systems, mostly including springs and spring elements, are commonly connected to static parts of the machine or vehicle, on one end, and in direct contact with the axle or other elements that provide a stable axis of rotation to the rotating mass or rotator. For example, a wheel that travels over a rough surface will transfer axial, vertical and other forces (e.g., impacts and/or vibratory) to the axle, which will be partially absorbed and diminished using suspension means that can be located between the axel and the chassis. Several attempts are known for implementing suspension mechanisms inside the wheels.
In recent years there is a growing trend towards more efficient self-propelled vehicles where the invested human power is transferred to movement of the vehicle with minimal energy loss. Modern wheelchairs and bicycles incorporate lightweight structural parts, wheels structures with improved strength-weight ratio, tires designed for minimized resistance to rolling, etc. There is also a preference of most riders to feel a rigid or responsive ride, rather than a soft one, especially when driving over substantially smooth surfaces and/or when riding upward inclines, and also when accelerating, decelerating or maneuvering. When suspension is implemented the manufacturers usually make some accepted tradeoffs between the physiological and improved comfort needs with the dynamic preferences of the users.
From GB 2 188 596, it is known to provide a wheel of a wheel chair with resilient spokes. These spokes are located non-radial so that the spokes can be flexed due to an impact. This wheel has the possible drawback that due to the high stress of the spokes, the spokes may break.
Another wheel having an implemented suspension mechanism inside the wheel is known from DE 10 2005 032 537. This car wheel has radial located spokes that are comprising an hydraulic damper. The possible drawback of the use of such dampers is that the damping characteristics by compressing the damper differ from the damping characteristics by elongating the damper. Since the wheel has a number of regularly located dampers, a damper being located opposite to the damper being compressed, has to be elongated. Due to the different damping characteristics, the rotation of the wheel becomes uneven. Furthermore, the dampers described in DE 10 2005 032 537 cannot be preloaded.